A. Field of Invention
The present invention relates to an apparatus for extending a bit or tool from its source of rotational power, and in particular, a bit or tool extension using tangential clamping and a single tool for operation of the clamping mechanism. In other forms, the invention can comprise a bit or tool clamp integrated with a machine, instead of any extension.
B. Problems in the Art
Previous extensions used a standard threaded collet design supplied with an extended shank to extend the reach of the bit when needed. They were supplied with internal or external threaded means to compress either the nut or a peripheral set of flexible fingers or a separate collet sleeve actuated by a nut threaded over the outside diameter of the extension body which, when tightened, compressed the fingers of the sleeve onto the bit shank, thereby retaining it. The previous methods require the use of two wrenches or the arbor lock of the router to tighten and release the bit shank in the extension. They also add an extreme amount of length to the shank, requiring a substantial spacer to be fabricated so as to return the useable stroke of the router. Also, due to the extreme length and slim profile, they are prone to introducing a substantial amount of concentric rotating whip into the spinning bit which the user would perceive as vibration both with the bit cutting and free running.
Other partial solutions are described in U.S. Pat. Nos. 3,091,474 and 5,348,319 and 5,096,212 and 6,332,619 B1. These allow single tool cutter changes without the use of the arbor locks or the factory tool wrench system. Disadvantages to these designs are difficulty in manufacturing and the inability to use standard and large shank bits. Also, the need for individual collets for each brand of router becomes apparent when the wide varieties of collet designs used by each manufacturer are taken into account. The collets do nothing to extend the reach of the cutter when it is needed, such as on a legacy mill. Special extra-long bits are needed for these machines which are hard to find and expensive when located. The eccentric sleeve used to clamp the bit is difficult to make and requires extreme care to ensure proper alignment and correct clamping. These sleeves are also oriented so that if the fastener should fail, the rotation of the bit shank will force the sleeve out of contact with the bit shank, therefore releasing the cutter from the machine. Another disadvantage to the eccentric sleeves used previously is they indent the shaft of the bit due to the low angular tangency. This can render the bit unusable. It can also prevent withdrawal of the bit from the collets. Other disadvantages to these designs are the difficulty of keeping the bore of the collets concentric with the centerline of the arbor due to the cone shape formed on the bottom of the collets to mate with the factory taper. Due to the clearance required to insert and remove the cutter when the bit is clamped in operating position, the centerline of the bit is no longer concentric with the center line of the arbor onto which it is mounted. They also have no means of retaining the bit in the collets when used in collets-down, vertical position. Assembly and repair is also hindered by the design of these chucks. The retention pins and spring rings used to hold the various components together are subject to catastrophic failure. If either the spring rings or retention pins fail, the collets are free to disengage from the machine arbor. Since the body of these tangential clamping designs is threaded, breaking the bolt off (broken piece remains in body) renders the collets useless and the end user would have to purchase another.